Proved carbonate rock fractured-vuggy carbonate reservoirs account for ⅔ of the reserves in the western region of China, and are one of the important fields for increasing reserve and production in China. Unlike sandstone oil reservoirs, fractured-vuggy carbonate reservoirs mainly comprise fractures and solution caves, and it is difficult to apply conventional deep oil reservoir control technology to fractured-vuggy carbonate reservoirs. A concept of flow channel modification for fractured-vuggy carbonate reservoirs was put forward and proved at mine sites in Tahe Oilfield, and it is proven that flow channel modification is an important measure to further solve the problems of planar waves and its limitations.
Up to now, pilot tests of flow channel modification with particle flow modifiers have been carried out for some fractured-vuggy carbonate reservoirs in China. The particle flow modifiers have attained excellent effects and exhibited a great potential in the pilot tests, but have the following drawbacks: (1) The difference in density between the particles and the water injected into the formation is too high: the particle flow modifiers used at present are mainly regenerated rubber particles, which have density much higher than the density of the water injected into the formation, tend to settle and may result in difficulties in injection and plugging near the well, and have a short effective distance; (2) the particles have to be carried by viscous fluid: since the particles tend to settle strongly, high-viscosity fluid is required to carry the particles, but such high-viscosity fluid can't adapt to the high temperature and high mineralization degree and loses its carrying ability essentially after it enters the formation; consequently, the effect of the measure is severely compromised, the overall construction cost is too high, and it is difficult to apply the measure widely at mine sites; (3) the particles have poor oil/water selectivity, and may cause severe damages to the formation and block the oil flow channels erroneously.